The invention relates to a device and a method for fresh-air supply of a turbocharged, reciprocating-piston internal combustion engine.
The fresh-air supply devices of the type which are the subject of the invention are used for boosting exhaust gas turbochargers. Particularly in the low speed range of a turbocharged, compression-ignition, reciprocating-piston internal-combustion engine, the connected exhaust gas turbocharger, for want of adequate drive energy, in most cases cannot develop the necessary charging pressure. These circumstances are brought to the attention of the driver when accelerating from a low speed, which is known as the so-called turbo lag effect. For compensation of this turbo lag effect, additional compressed air from a compressed air supply of the motor vehicle is fed into the intake pipe of the reciprocating-piston internal-combustion engine in the requirement situation. Many motor vehicle types, such as commercial vehicles or omnibuses, in any case have a compressed air system available, from which inter alia the pneumatic brake system is supplied.
A generic-type fresh-air supply device for a turbocharged, reciprocating-piston internal-combustion engine follows from WO 2005/064134 A1. The charging air which is compressed by means of an exhaust gas turbocharger, reaches the cylinder chamber via an intake pipe in the same manner as an exhaust gas recirculation (EGR). Furthermore, a compressed air pipe leads into the side of the intake pipe and via a valve is opened or closed in an electronically controlled manner. In order to compensate the turbo lag effect, the valve is opened so that the external compressed air, which in this case is extracted from the compressed air accumulator of the compressed air system, reaches the intake chamber. In order to avoid backflowing of this additionally fed compressed air a force-actuated check valve is arranged in the intake pipe downstream of the turbocharger.
This check valve can be formed as a butterfly valve in the intake pipe. The force-actuation of a butterfly valve, which is arranged in the intake pipe, is resolved in a customary manner by an electronically-controlled electric motor. For diesel engines with an EGR device, it is proposed in U.S. Pat. No. 4,624,228 to arrange a butterfly valve in the intake pipe which during cold start of the diesel engine is operated in the closing direction, otherwise it is fully opened during normal operation.
It is an object of the present invention to create an efficient fresh-gas supply device for turbocharged, reciprocating-piston internal-combustion engines which are provided with an EGR device, and which is equipped with a compressed-air injection device and which can be universally used in turbocharged, compression-ignition, reciprocating-piston internal-combustion engines.
According to the invention, a butterfly valve is controlled in the fresh-gas supply device so that it is equally suitable as a control valve for the compressed-air injection device and for the EGR device, that is to say that the operation of the butterfly valve can fulfil the two control requirements of the reciprocating-piston internal-combustion engine. It is furthermore an advantage of the invention to improve the accelerating and emissions behavior of the turbocharged, reciprocating-piston internal-combustion engine by the common controlling/regulating of the compressed-air injection device and of the EGR device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.